Unlocking

I currently have a tab with koodo atm, I still really like my phone, but I'm planning on getting one for my little brother..I probably have around 200 left on my tab. If I were to buy a s3 for 150 (using my account) from the store, would it still count towards my tab, and would I be able to unlock it whenever I like? Also, there's a promotional thing where koodo pays me 100 dollars to upgrade my phone, will it still apply if I'm paying retail price for it?